Sharif Digital Repository

Axial flux resolvers (AFRs) are used in motion control of electrical machines. In this paper, the effects of physical parameters on the accuracy of detected position are studied. The examined parameters are width of slot opening and slot width, number of poles, number of slots per pole and per phase, and skewing of rotor slots. An analytical model based on the winding function method is proposed for the first time in to estimate the error of position signal. The results of the analytical method are verified with 3-D time stepping finite-element method. Finally, the prototype of the studied AFR is constructed and tested. Good agreement between simulation and experimental results confirms the... 

Linear permanent magnet machines are increasingly used in industrial applications where they need position sensors to improve their performance. Variable Reluctance resolvers are one the best position sensors that can be used in unfriendly environment conditions, with high mechanical vibration, wide temperature variation and polluted environments. However, conventional VR resolvers suffer from complicated winding process, undesirable performance under eccentricities, and high position error in two-pole applications. So, in this paper a new linear resolver is proposed based on the sinusoidal variation of common area between the moving and the stationary parts. Then, the influence of... 

Employing Multi-Turn Wound-Rotor (WR) resolvers are suggested for applications that high accuracy and absolute measurement are required, simultaneously. Conventional multi-turn resolvers are consisted of two individual resolvers in a common frame and suffer from high cost and big size that has a loading effect on the driven machine. Those challenges are over-come in proposed structures of recent researches in the price of a complicated winding process in manufacturing where the aim of this paper is laying. To find the best solution, an index is proposed and calculated. All the simulations are done using time-stepping finite element analysis (TSFEA). Then, the prototype of the optimal... 

Linear position sensors are essential parts of linear motion control systems. Among different linear sensors, linear resolvers are an appropriate choice for harsh environments. Design optimization of linear resolvers needs an accurate, but computationally fast model for their performance prediction. Slotting effect of the cores and end effect are two important phenomena that must be accurately involved in the model to ensure its reliable results. Therefore, in this paper a semi-analytical model based on subdomain modeling technique is proposed for linear resolvers. Then, according to the developed model, the induced voltages in the signal windings of the resolver are calculated and... 

Multi-turn resolvers are employed in the applications that high reliability; high accuracy and absolute position measurement are required, simultaneously. They are basically consisted of two individual resolvers in a common frame. In this paper a novel sinusoidal air-gap length multi-turn resolver is proposed. The rotor shape and the winding configuration are designed to achieve single-speed and multi-speed operations using a single rotor and a single stator core. Furthermore, some constraints are laid down and discussed in such a way that the performance of two resolvers has no interference with each other. All the mathematical calculations are validated using time stepping finite element... 

Wound-Rotor (WR) resolvers are similar to two-phase synchronous generators. Their difference is related to the excitation signal. While DC voltage is used for exciting synchronous generator, high frequency AC voltage is employed for that of resolver. The common waveform for excitation signal of resolver is sinusoidal voltage. However, preparing the high frequency sinusoidal voltage in the resolver to digital converter (RDC) is always a challenge. Therefore, in this paper different high frequency AC waveforms are applied as the excitation signal of the resolver and the estimated position, resulted from RDC, is discussed. The aim of this work is to find an appropriate excitation waveform that... 

Multi-turn resolvers are consisted of two individual resolvers in one housing. Due to use of both single speed and multi-speed resolvers in one frame, multi-turn resolvers are supposed to provide the benefits of higher accuracy and absolute position measurement, simultaneously. In this paper, after presenting different configurations of wound-rotor (WR), multi-turn resolvers, their design considerations are discussed. Winding function (WF) method is used for finding appropriate slot-pole combinations, and winding configurations. Then time stepping finite element analysis is applied to evaluate the performance of the designed resolvers. Finally, experimental measurements validate the... 

In this paper we highlight a remarkable difference between the step responses of a classical second-order transfer function and its fractional-order counterpart. It can be easily shown that the step response of a stable classical second-order transfer function crosses its final value infinitely over time. In contrast, it is illustrated here that the step responses of a fractional-order counterpart of the classical second-order model possess only a finite number of such crossovers. In other words, for such a system one can find a specific time instant after which the step response is over or under-convergent to its final value. This property interprets some phenomena observed in the... 

Position sensors are inseparable part of motion control systems. Linear resolvers (LRs) are electromagnetic position sensors that are suitable for high vibration, polluted environments. The accuracy of their detected position can be affected by different mechanical faults. In this study, variety of possible mechanical faults along with their mathematical index in LRs is introduced. Static eccentricity, dynamic eccentricity, inclined mover and run out error are the presented mechanical faults that are discussed independently and simultaneously. Then, three-dimensional non-linear, time-stepping finite element method is employed to investigate the performance of the studied resolver under... 

In this study an analytical model based on solving Maxwell equations in the machine layers is presented for linear resolver (LR). Anisotropy, field harmonics, slot effects, number of slots per pole per phase and the effect of tooth skewing are considered in the model. The proposed method is a design oriented technique that can be used for performance prediction and design optimisation of the LR due to its acceptable accuracy and fast computation time. Two- and three-dimensional time stepping finite element method (FEM) is employed to validate the results of the proposed model. Good correlations between the results obtained by the proposed method and the FEM confirm the superiority of the... 

The axial flux brushless resolver without rotor windings is newly proposed resolver that has the advantages of variable reluctance (VR) resolvers for having no winding on rotor and also, its manufacturing process is much simpler than that of VR resolvers. The influence of different mechanical faults on the position error of the studied resolver is discussed. Different types of eccentricities, inclined rotor and run out error independently and simultaneously are studied using 3D time stepping finite-element method. The results show the maximum position error is related to the resolver under static eccentricity (SE), so an optimised rotor is proposed for the studied resolver to overcome this... 

In this study, a new 12-slot two-saliency variable reluctance (VR) resolver with simple non-overlapping windings is proposed. The excitation winding in the proposed resolver is replaced with one axial coil that is perpendicular to the signal windings. Both distributed and non-overlapping concentric windings with uniform coil turns are used. The rotor has two upper and lower saliencies located in front of each other. The shape and width of each saliency are determined based on the optimisation. Compared with conventional 12-slot VR resolvers, the proposed resolver has a simpler rotor structure and the advantages of two-saliency resolvers against eccentricity, absolute output position, and... 

Variable reluctance (VR) resolvers have some distinguish features over wounded rotor resolvers that make them suitable for industrial applications. Among different types of VR resolvers, sinusoidal-rotor resolvers are preferred due to simple structure and high performance under eccentricities. However, their accuracy is affected by inevitable run-out error. As they work based on sinusoidal variation of coupling area between stator and rotor and under run-out error the coupling area is impaired. Hence, in this study, a new disk shape configuration is proposed for sinusoidal-rotor resolver that is robust against run-out error. Geometrical dimensions are calculated based on optimisations to... 

An unconditionally stable fully explicit finite difference method for solution of conduction dominated phase-change problems is presented. This method is based on an asymmetric stable finite difference scheme for approximation of diffusion terms and application of the temperature recovery method as a phase-change modeling method. The computational cost of the presented method is the same as the explicit method per time-step, while it is free from time-step limitation due to stability criteria. It robustly handles isothermal and nonisothermal phase-change problems and is very efficient when the global temperature field is desirable (not accurate front position). The robustness, stability,... 

Resolver, as an electromagnetic sensor, is widely used in different industrial applications such as servo motor feedback applications because of its reliable performance in the presence of undesired external factors in a harsh environment. Among different types of resolvers, variable reluctance (VR) resolvers draw attention due to their robust structure with a winding-less solid rotor and low-cost manufacturing. In this article, analytical modeling based on the magnetic equivalent circuit (MEC) is employed to investigate the output signals of the proposed toroidal winding arrangements for VR resolver with a 5-X rotor. Time-stepping finite element analysis (TSFEA) is used for all the... 

In this paper static eccentricity (SE) fault diagnosis in wound rotor (WR) resolver is considered and a new noninvasive index is proposed. Using the proposed index not only leads to SE detection but also, helps to precisely determine the eccentricity level. Furthermore, the location of the fault is determined using two search coils. In this regard, a mathematical model based on the winding function method is proposed. In the proposed model the influence of non-uniform air-gap length on calculating the inductances is considered. Then, time-stepping finite element method (TSFEM) is used for approving the success of the proposed index. Finally, experimental tests are done to validate the... 

A common solution for increasing the accuracy of wound-rotor (WR) resolvers is to increase the number of poles. To achieve a compact design, fractional slot concentrated winding is used for multi-pole WR resolvers. However, employing such windings leads to rich sub-harmonics in the induced voltages. To suppress these undesirable sub-harmonics, multi-layer windings with appropriate shifting angle between the layers is suggested. However, the said shifting angle is limited by the slot pitch so that the capability of the multi-layer winding is not utilized fully. To overcome the mentioned deficiency a slotless disk type configuration is proposed in this paper. Then, an optimization based on the... 

Winding configuration is a crucial factor that highly affects the accuracy of resolvers. A nonoptimal winding could also make the manufacturing process complicated and costly inefficient. In this article, an approach to determine the optimal winding configuration for the resolvers is proposed. This method is applicable for both wound rotor (WR) and variable reluctance (VR) resolvers, and significantly simplifies the winding configuration of resolvers with different pole pairs and teeth numbers. Based on the proposed approach, the winding configuration of multiturn resolvers, which are generally more complicated than single-turn resolvers, is simplified for WR and VR type resolver with... 

Variable Reluctance (VR) resolver is an angular position sensor that is commonly used in the automotive industry. In this paper, A general method for determining the winding configuration of VR resolvers is proposed, that eases the manufacturing process. At first, the operational principle of conventional winding has been presented using mathematical formulations. Following that, the non-overlapping tooth coil winding method, as the ideal winding option for VR resolver, has been extended that can be applied to the VR resolver with arbitrary poles and stator tooth numbers. The method of determining the reference and signal windings presented and used to determine the winding for a 2, 6, and 8...